1. Field of the Invention
This invention relates to bicycle suspension systems, particularly to a lightweight highly responsive off-road racing bicycle front wheel suspension system, although the invention is adaptable to rear suspension and to paved road racing bicycles.
2. Prior Art
Racing bicycle suspension systems require a combination of construction features which place a high priority on low weight, rigidity, responsiveness, and producibility. In today's bicycle racing environment, a few ounces of additional weight, a small amount of "play" in the system, and/or a lack of responsiveness to various terrains means the difference between winning or losing a race. A superior athlete can generate less than one horsepower and this small amount of power must be wisely used. Since the addition of suspension adds weight to the bicycle, the ability of the suspension to give the rider increased control in high speed downhill maneuvers must more than compensate for the weight increase which slows uphill pedaling. Thus weight considerations and responsiveness must be perfectly balanced. Ideally, a bicycle suspension system would also instantaneously adjust itself to the widely varying terrain encountered in "mountain bike" racing, and the spring and damping rates would increase with wheel travel.
In prior art inventions, especially those which draw upon dual shock motorcycle technology, one problem is solved while another is created. Systems which tend to give best damping control tend to be heavy, such as a dual shock absorber system using common coilspring/hydraulic viscous damping. Such dual fork shock absorber systems work well on dirt track motorcycles where power to weight ratios are much greater than on bicycles. Lighter weight is achieved in dual fork systems, such as one marketed by Answer Racing Products of Valencia, Calif. called the "Manitou" by utilizing viscoelastic materials that serve as springs and provide some damping due to friction between the molecules of the material; however, these materials tend to break down in a relatively short time. Also, dual fork shock absorber systems have the disadvantage of having to be synchronized to work together in order to prevent brake rub. Steering rigidity tends to be low because the wheel axle provides the only resistance to twisting moments induced in the shock tubes by steering forces. In a mono-shock absorber system, rigidity problems and weight are reduced by enclosing a viscous damping system in the bicycle head tube and using compressed air as the spring such as in the "Delta V" shock absorber made by Cannondale Corporation of Bedford, Pa. The latter system is an improvement, but is not instantaneously self adjusting in that the spring and damping rate do not vary with wheel travel. Further, although an air spring is the lightest means of providing spring force, the air spring must always have a relatively large initial pressure and is subject to leakage. There is a monoshock absorber system utilizing steel springs made by ACTION-TEC Company of Silverado, Calif., but it is relatively heavy and not self adjusting.